The present invention relates to a valve mechanism, particularly to a valve mechanism which can be used for a tube-type fluid container.
In this type of tubular container, recently, instead of conventional tubes comprising a metal or an aluminum-foil-laminated material, tubes comprising a synthetic resin alone or a lamination of a synthetic resin and aluminum (hereinafter referred to as “synthetic resin made” materials) have been used.
In the case of a tube-type container using a synthetic resin made tube, because these synthetic resin made tubes have elasticity recovering force, the following problem occurs: When the pressure is released after a fluid is discharged by pressing the tube, air flows back from an opening portion for discharging the fluid to the fluid storing portion due to the elasticity recovery of the tube, contributing deterioration of the quality of the fluid stored.
For this reason, a tube-type container, in which a tabular valve body is provided in an opening portion for discharging the fluid and the opening portion is closed by this valve body when the shape of the tube is elastically restored, has been proposed (e.g., Japanese Patent Laid-open No. 1995-112749, Japanese Patent Laid-open No. 1998-157751, Utility Model Registration Application No. 1984-26748, etc.).
Thus, in the conventional tube-type container in which the above-mentioned tabular valve body is provided, if the tube recovers its original shape by its elasticity slowly, the valve body fails to close the opening portion of the tube-type container and air may flow back to the fluid storing portion.
Additionally, the conventional tube-type container in which the above-mentioned tabular valve body is provided, has a problem in its low durability.
Further, in the above type of valve mechanism, conventionally, as described in the Japanese Patent Laid-open No. 2001-179138, a valve mechanism having a spherical valve body and a spring for giving momentum to the valve body toward a valve seat has been used.
Manufacturing the valve mechanism using the spherical valve body and the spring, however, tends to be very expensive. Consequently, a valve mechanism, which has a valve seat, and a valve body which moves between a closed position in which the valve body is in contact with the valve seat and an open position in which the valve body is separated from the valve seat, is commonly used.
In this valve mechanism, it is preferred that the valve mechanism can close a fluid reliably although its configuration is simple. Additionally, it is preferred to provide a configuration which can change a flow rate of the fluid passing through it discretionally according to a pressure applied to the fluid. As matters stand, however, a valve mechanism possessing these requirements has not been reported.